Abstract

Chemical analysis of potential pollutants in wastewater is hampered by the large number of toxins, time constrains and high costs. Therefore bioassays are being employed to evaluate toxicity and monitor pollution levels. In addition to protozoa, invertebrates and vertebrates as well as algae and higher plants, flagellates are being used for this purpose. Euglena gracilis, a unicellular photosynthetic flagellate, is an excellent candidate because of its ease of cultivation, fast growth and rapid responses to environmental stress parameters. The cells are motile and respond to light and gravity and are capable of morphological changes of their cell form. The precision of phototaxis and gravitaxis is affected by a variety of organic and inorganic toxins. Swimming velocity and percentage of motile cells is a sensitive endpoint for pollution monitoring. Photosynthetic quantum yield and pigments are likewise suitable parameters in testing environmental stress parameters.